New Cluster Moments for Jet Cleaning Atlas Reco meeting Sven Menke, - PowerPoint PPT Presentation

New Cluster Moments for Jet Cleaning Atlas Reco meeting Sven Menke, MPP M¨ unchen 4. Oct 2011, CERN � Definition of the new cluster moments � Example distributions � Use for jet cleaning �

Definition of the new cluster moments � Some quantities for jet cleaning are still calculated on the CaloCell level � Most notably the quality and the amount of negative energy could so far not be extracted from clusters on the AOD � The following new moments make this information now available on AODs, such that jet cleaning code can be written to use clusters and not cells: • BADLARQ_FRAC : the energy fraction inside the cluster carried by cells with a quality larger than Q min (4000 by default) • ENG_POS : the sum of the energies of all positive cells • SIGNIFICANCE : the ratio of the cluster energy over the cluster noise: �� σ noise , where the sum runs over all cells E clus / unchen � New Cluster Moments for Jet Cleaning � S. Menke, MPP M¨ Atlas Reco meeting, 4. Oct 2011, CERN 2

Example distributions 3 10 � Plots are from 1000 single pion MC 2 10 events (3820 clusters) � Only one cluster had bad quality – and 10 the fraction is 1 . 4. 1 0 0.2 0.4 0.6 0.8 1 1.2 1.4 c.getMomentValue(CaloClusterMoment::BADLARQ_FRAC) • it’s larger than 1 because it had − 260 MeV negative and + 610 MeV positive energy – i.e. the bad cell had 3 10 + 500 MeV 2 10 � Positive energy (in MeV) reflects the 10 simulation of pion energies flat in log E 1 3 10 × � Significance is on average 3 orders of 0 200 400 600 800 1000 1200 1400 1600 1800 c.getMomentValue(CaloClusterMoment::ENG_POS) magnitude smaller than energy in MeV • signals above 1 GeV start to be 3 10 significant 2 10 • but this depends of course on the 10 region in the calorimeter 1 0 200 400 600 800 1000 1200 1400 1600 c.getMomentValue(CaloClusterMoment::SIGNIFICANCE) unchen � New Cluster Moments for Jet Cleaning � S. Menke, MPP M¨ Atlas Reco meeting, 4. Oct 2011, CERN 3

Use for jet cleaning � For jet cleaning the sampling fractions and time can be computed as before since all 24 sampling energies and the cluster time are available on AOD � Jet quality fraction can be computed like so: clusters f cluster × E em − scale / E em − scale f jet = � cluster jet � If different regions (EM/HEC) need to be distinguished the λ center moment of the cluster and its η can be used to compute the region it is in � Negative jet energy can be computed like so: E neg − E pos clusters E em − scale jet = � cluster cluster � More info is on the Twiki: ClusterMoments unchen � New Cluster Moments for Jet Cleaning S. Menke, MPP M¨ Atlas Reco meeting, 4. Oct 2011, CERN 4